JP3412593B2 - Non-reciprocal circuit device and high-frequency circuit device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonreciprocal circuit device such as an isolator used in a microwave band and the like and a high frequency circuit device such as a communication device using the nonreciprocal circuit device.

[0002]

2. Description of the Related Art A non-reciprocal circuit device used in a microwave band or the like is disclosed in US Pat.
-134349, JP-A-58-3402, JP-A-9-232818 and JP-A-8-8612.

The non-reciprocal circuit element is an element in which center electrodes intersecting at a predetermined angle are provided on a ferrite plate and a static magnetic field is applied to the ferrite plate. By rotating the plane of polarization of the high-frequency magnetic field generated by the Faraday rotation principle, an irreversible characteristic is generated.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As in the above non-reciprocal circuit device, the one using the first to third center electrodes,
Since the matching impedance of the third center electrode has a reactance component and the impedance depends on the frequency, the frequency range in which good irreversible characteristics are obtained becomes narrow. That is, the isolation characteristic when used as an isolator is inevitably a narrow band.

Further, the non-reciprocal circuit device using the two center electrodes is advantageous for downsizing and widening the band, but is used for a communication device in response to the recent demand for downsizing the communication device in a wireless communication system. Further miniaturization is also required for nonreciprocal circuit devices such as isolators.

However, when the ferrite plate is greatly downsized to 0.5 mm × 0.5 mm × 0.3 mm with the conventional structure, the length of the center electrode becomes short as described below. The inductance component becomes small, and impedance matching cannot be achieved when operating at a desired frequency, resulting in a large insertion loss (IL).

The circuit diagram of the conventional isolator is as shown in FIG. 8. However, when the inductance of the center electrodes L1 and L2 is impedance-matched by the capacitance of the parallel capacitors C1 and C2, the impedance locus is shown in FIG. The relationship is as shown in. That is, when the impedance of the central electrode is a certain value, etc. Con to match the normalized impedance (50 [Omega) by connecting a parallel capacitor, the impedance of the center electrode through a 50 [Omega
Must be on the ductance circle.

However, the size of the isolator is 3.5.
If the size is about mm × 3.5 mm × 1.5 mm or less, the size of the ferrite plate becomes 1.0 mm × 1.0 mm × 0.3 mm or less in the case of a rectangular parallelepiped. In the structure in which the center electrode is arranged only on the main surface side of the ferrite plate like the conventional isolator, the inductance of the center electrode becomes small. Therefore, since the reactance at the operating frequency becomes small, the capacitance of the parallel capacitor for matching must be increased. However, as a result, there arises a problem that the operating frequency bandwidth becomes narrow.

Further, if a single-plate capacitor is used as the matching parallel capacitor, its size also becomes large, and the target size of the isolator cannot be realized.
For example, in an attempt to design an 800 MHz band isolator having an outer size of 3.5 mm, when the center electrode has an inductance of 6.6 nH, the parallel capacitor needs to have a capacitance of 6 pF. For example, the relative permittivity is 1
10 high-dielectric-constant ceramic plates with a thickness of 0.17 m
Even if it is as thin as m, its capacitor size is 1.0 × 1.
It becomes as large as about 05 mm, and it becomes impossible to accommodate it in the target size. In addition, the central electrode is reduced in size as the overall size is reduced, and its inductance is reduced.
If the impedance of the center electrode does not ride on the equal conductance circle passing through the normalized impedance (50Ω), impedance matching cannot be achieved even if the capacitance of the parallel capacitor is increased, the input / output impedance becomes high, and the insertion loss deteriorates. To do. An object of the present invention is to provide a non-reciprocal circuit element that exhibits non-reciprocal characteristics over a wide band, has a small insertion loss, and a high-frequency circuit device such as a communication device using the non-reciprocal circuit element.

[0010]

SUMMARY OF THE INVENTION According to the present invention, first and second center electrodes which are grounded at their respective ends and which intersect each other, and a ferrimagnetic material which is adjacent to the first and second center electrodes,
A magnet for applying a static magnetic field to the ferrimagnetic material;
A series capacitor connected in series between the other end of the second center electrode and the input terminal and the output terminal;
The other end of the parallel capacitor connected in parallel between the ground of the second center electrode, consisted city, the first and
The second center electrode is wound around the ferrimagnetic material,
Impedance of the first and second center electrodes seen from the other end
Is a Smith chart whose center is the normalized impedance
Isoconductance larger than the isoconductance circle passing through the center of
While riding on the drawer circle,
From the connection position of the parallel capacitor
The impedance seen from the center electrode is
On the top of the center electrode from the impedance position of the center electrode
Direction toward the center of the Smith chart along the chest circle
Move to the input by connecting the series capacitor
The impedance seen from the terminals and output terminals is
From the impedance position due to the connection of the column capacitor
Along the circle of equal resistance of the Smith chart
The parallel capacitor and the series to move to the center
It is characterized by setting the capacity of each capacitor
It

With this structure, a small ferrimagnetic material is used.
The inductance of the first and second center electrodes
A sufficient value is secured, and the input and output impedances are matched by the series capacitor and the parallel capacitor to reduce the insertion loss.

[0012]

Further, according to the present invention, the intersecting angle of the first and second center electrodes is set to a predetermined angle within the range of 80 to 100 degrees. This gives the desired irreversible properties.

Further, according to the present invention, the ferrimagnetic material has a polygonal plate shape. As a result, the magnetic coupling distance between the first and second center electrodes with respect to the ferrimagnetic material of the first and second center electrodes is increased. Further, when winding the first and second center electrodes around the ferrimagnetic material, the winding is facilitated.

Further, according to the present invention, the magnet has a rectangular parallelepiped shape. As a result, in the non-reciprocal circuit element having a rectangular parallelepiped shape as a whole, the strength of the static magnetic field with respect to the ferrimagnetic material is further increased within a limited volume.

Further, according to the present invention, the first and second center electrodes, the ferrimagnetic material and the magnet are arranged between the upper yoke and the lower yoke, and the upper yoke and the lower yoke are grounded. With this structure, the first and second center electrodes, the ferrimagnetic material, and the magnet are grounded and shielded.

Further, the present invention constitutes a high frequency circuit device such as a communication device by using any one of the above non-reciprocal circuit elements and by providing the non-reciprocal circuit element in the output part of the oscillation circuit or the input part of the filter.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The configuration of an isolator according to a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a circuit diagram of an isolator. Here, 10 is a rectangular parallelepiped-shaped ferrite plate, and the 1st center electrode 11 and the 2nd center electrode 12 which consist of each insulated copper wire which cross | intersect at a predetermined angle mutually with respect to the ferrite plate 10 are provided. It's wrapped around. First and second center electrodes 1
One end of each of 1 and 12 is grounded, and a series capacitor C is provided between the other end of the first center electrode 11 and the input terminal and between the other end of the second center electrode 12 and the output terminal.
21 and C22 are connected in series. In addition, a parallel capacitor C is provided between the other end of the first center electrode 11 and the ground and between the other end of the second center electrode 12 and the ground.
11 and C12 are connected in parallel. further,
A resistor R is connected between the other ends of the first and second center electrodes 11 and 12. Although not shown in this figure, a static magnetic field is applied to the ferrite plate 10 in its thickness direction (direction parallel to the loop surface formed by the first center electrode 11 and the second center electrode 12). The magnet is arranged.

FIG. 2 is an exploded perspective view of the isolator constituting the above circuit. Here, reference numeral 1 denotes a ferrite assembly in which a first center electrode 11 and a second center electrode 12 each made of an insulation-coated copper wire are wound around a ferrite plate 10 for 1.5 turns respectively. Reference numeral 3 is a magnet that applies a static magnetic field to the ferrite plate 10, and reference numerals 2 and 4 are an upper yoke and a lower yoke which respectively form a part of a magnetic circuit. Reference numeral 5 is a substrate, on the upper surface of which a ground electrode 50 and an input terminal electrode 51
And the output terminal electrode 52 is formed. A part of these electrodes extends to a part of the lower surface via the end face of the substrate 5, and is used as a terminal electrode when the isolator is surface-mounted on the circuit board of the electronic device. C11, C1
Reference numerals 2, C21, C22 and R are chip parts constituting the capacitors and resistors of the respective parts shown in FIG. 1, of which C11, C12 and R are mounted on the lower yoke 4. Further, C21 and C22 are mounted on the upper surface of the substrate 5.

FIG. 3 is a perspective view showing a state in which the components shown in FIG. 2 are assembled and the upper yoke 2 and the magnet 3 are removed. In this way, the lower yoke 4 is joined to the ground electrode 50 formed on the upper surface of the substrate 5 by soldering or the like, and the capacitors C11, C12 and the ferrite assembly 1 are joined to the upper surface of the lower yoke 4 by soldering or the like. The capacitors C11 and C12 are chip capacitors having electrodes provided on the upper and lower surfaces thereof, and the electrodes on the lower surface are soldered to the upper surface of the lower yoke 4. Further, one ends of the center electrodes 11 and 12 of the ferrite assembly 1 are electrically connected to the upper surface of the lower yoke 4 by soldering. Furthermore, the other ends of the center electrodes 11 and 12 are capacitors C11 and C, respectively.
Soldered to the electrodes on the upper surface of 12. Further, the electrodes on both ends of the resistor R are soldered to the electrodes on the upper surfaces of C11 and C12. The ferrite plates 10 of the center electrodes 11 and 12
Since the surface of the winding portion for is wound with an insulating coating, the center electrodes are electrically insulated from each other and the center electrode and the lower yoke 4 are electrically insulated from each other.

The capacitors C21 and C22 are also provided with electrodes on the upper and lower surfaces, and the electrodes on the lower surfaces are soldered to the input terminal electrodes 51 and the output terminal electrodes 52 of the substrate 5, respectively. The electrodes on the upper surfaces of C21 and C22 and C1
Wires w are soldered between the electrodes on the upper surfaces of C1 and C12.

The magnet 3 shown in FIG. 2 is attached to the top surface of the upper yoke 2, and by covering the lower yoke 4 with the upper yoke 2 to which the magnet 3 is attached, a closed magnetic path is formed.

The dimensions of the ferrite plate 10 shown in FIGS. 1 and 2 are 0.5 mm × 0.5 mm × 0.3 mm. The substrate 5 has a thickness of 0.1 mm, the lower yoke 4 has a thickness of 0.15 mm, and the upper yoke 2 has a thickness of 0.15 mm.
mm, and the diameter of the center electrodes 11 and 12 is 0.05 mm.

For example, in a communication device used in a mobile communication system such as a mobile phone, the height dimension of the isolator should be 1.5 mm or less in order to sufficiently reduce the occupied area (volume) in the device. Although it is a market requirement, the height dimension is kept to 1.5 mm or less due to the above structure and the dimensions of each part. By the way, when the thickness of the ferrite plate 10 is increased with the dimensions of each part other than the ferrite plate unchanged, the total height can be suppressed to 1.5 mm up to a thickness of 1 mm. Therefore, in order to make the ferrite plate as large as possible within the limited volume, it is sufficient to form a rectangular parallelepiped whose corners have a dimension of 1 mm or less.

FIG. 4 is a circuit diagram for explaining the operating principle of the isolator. In FIG. 4, arrows indicate the directions of the high-frequency magnetic fields below the center electrodes 11 and 12. Now, considering the transmission of signals in the forward direction, as shown in FIG.
Both ends of the resistor R have the same phase and the same amplitude, no current flows through the resistor R, and the input signal from the input terminal is directly output from the output terminal.

Considering the incidence of signals in the opposite direction, as shown in (B), the direction of the high-frequency magnetic field passing through the ferrite plate 10 is opposite to that in the case of (A), and both ends of the resistor R are connected. A signal having a reverse phase is generated and power is consumed by the resistor R. Therefore, ideally, no signal is output from the input terminal.
Incidentally, the circuit from which the resistor R is removed acts as a gyrator.

In practice, the phase difference between the both ends of the resistance between the forward transmission of the signal and the reverse incidence of the signal depends on the intersection angle of the center electrodes 11 and 12 and the rotation angle of the plane of polarization due to Faraday rotation. Change. Therefore, the crossing angle between the central electrodes 11 and 12 and the strength of the external magnetic field is determined so that the insertion loss is small and high irreversibility (isolation characteristic) is obtained. The strength of the magnetic field applied to the ferrite plate is usually 0.09 to 0.17 [T], and the rotation angle of the plane of polarization due to Faraday rotation is usually 90 to 100 degrees. When the crossing angle is set within the range of 90 degrees to 100 degrees, insertion loss is small and high irreversibility (isolation characteristic) is obtained.

The above operation is premised on that the input / output impedance and the isolator impedance are matched. However, if the ferrite plate is significantly downsized to, for example, 0.5 mm × 0.5 mm × 0.3 mm with the conventional structure, as described above, the length of the center electrode is shortened, and its inductance component is reduced. It becomes so small that impedance matching cannot be achieved when operating at a desired frequency.

Therefore, as shown in FIG. 1 and FIG.
The center electrodes 11 and 12 are wound around the ferrite plate 10. As a result, even if a small ferrite plate is used, the inductance of the center electrode is greatly increased and the operating frequency band is widened. However, since the increase in the inductance due to the winding of the center electrode is rapid, the normalization impedance (50
Ω), resulting in a case where a match cannot be obtained. Therefore, as shown in FIGS. 1 and 2, a series capacitor is connected in series to the input / output terminal.

FIG. 5 is a diagram showing an example of impedance matching by the parallel capacitor and the series capacitor.
(A) is an example when the inductance of the center electrode is relatively small, and (B) is an example when the inductance of the center electrode is relatively large. In either case, the connection of parallel capacitors moves the combined impedance on the equal conductance circle, and the connection of series capacitors causes
The value of the parallel capacitor and the series capacitor is determined so that the combined impedance moves on the circle of equal resistance and finally matches the normalized impedance (50Ω).

Thus, in the 2-port isolator to which the gyrator having two center electrodes is applied,
In order to optimize the phase rotation angle of the gyrator, the strength of the static magnetic field applied to the ferrite plate may change frequently, but this changes the permeability of the ferrite,
The inductance of the center electrode also changes. Even in such a case, impedance matching can be easily achieved by changing the capacitances of the parallel capacitor and the series capacitor without changing the shape of the center electrode. Therefore, it is easy to design or adjust the above optimization.

Furthermore, in an impedance matching circuit using two capacitors, a parallel capacitor and a series capacitor, the capacitance of the capacitor can be significantly reduced compared to the case where only one parallel capacitor is used. The size when the capacitance is formed can be reduced.
For example, when the inductance of the center electrode wound around the ferrite plate is 19.8 nH, the capacitance of the parallel capacitor is 0.5 to 1.5 pF, the capacitance of the series capacitor is 0.5 to 2.2 pF, and the relative permittivity is Using 110 dielectric materials, the thickness is 0.17 mm and the width is 0.45 x
It becomes 0.85 mm or less. Therefore, if a ferrite plate having a size of 1 mm square or less is used, the size of the isolator having a size of 3.5 mm square or less can be realized.

The series capacitor or the parallel capacitor may be composed of a chip capacitor having a laminated structure in which a plurality of electrode layers and dielectric layers are alternately laminated. In that case, since the chip capacitor is further downsized, by winding the center electrode around the ferrimagnetic material, even if the inductance of the center electrode becomes too large, a large capacity of the series capacitor or the parallel capacitor is secured, Impedance matching can be easily achieved, and the miniaturization of the entire nonreciprocal circuit device is further facilitated.

FIG. 6 is a diagram showing frequency characteristics of the insertion loss and the input impedance of the isolator. Here, the center frequency is designed to be 2.52 GHz.
(A) the frequency is 2.02 GHz to 3.02 GHz
Transmission characteristics S21 and reflection characteristics S when changed to
12 losses are shown. Further, (B) shows the locus of the input impedance due to the frequency change. In this way, the input / output impedance is matched with the normalized impedance (50Ω), so that a low insertion loss characteristic is exhibited.

Incidentally, in the conventional isolator in which matching is achieved only by the parallel capacitor, when the inductance becomes too large due to the winding of the center electrode around the ferrite plate, the input impedance becomes high as described below. There is no matching, and the insertion loss becomes worse. FIG. 10 is a diagram showing frequency characteristics of insertion loss and input impedance of the isolator. As in the case of FIG. 6, the center frequency is designed to be 2.52 GHz. (A) shows the frequency from 2.02 GHz to 3.
The loss of the transmission characteristic S21 and the reflection characteristic S12 when changed to 02 GHz, (B) show the loci of the input impedance due to the frequency change. Thus, if the inductance of the center electrode becomes too large, the input / output impedance becomes high and the insertion loss becomes
It becomes very bad at about 10 dB.

On the other hand, as shown in FIG. 5, impedance matching is achieved by the parallel capacitor and the series capacitor, so that the insertion loss in the example of FIG.
It can be improved to about 1.6 dB.

Next, the configuration of a high frequency circuit device such as a communication device and a signal measuring circuit will be described with reference to FIG. Using the above various isolators, for example, as shown in FIG. 7A, an isolator is provided in the oscillation output part of an oscillator such as a VCO, and a reflected wave from a transmission circuit connected to the output part of the isolator is transmitted to the oscillator. Do not let it enter. This improves the oscillation stability of the oscillator.

Further, as shown in FIG. 7B, an isolator is provided at the input part of the filter and the isolator is used for matching. This constitutes a constant impedance filter. Such a circuit is provided in the transmission / reception circuit section to form a communication device.

In each of the above-described embodiments, an example of using as an isolator is shown. However, when a gyrator (non-reciprocal phase shifter) having a characteristic in which the phase delay differs depending on the transmission direction between the two ports is used. In this case, the resistance R shown in the embodiment may be removed.

In the examples shown above, the linear center electrode is wound around the ferrite plate, but the sheet material having the center electrode pattern is arranged so as to overlap the ferrite plate, or the above-mentioned sheet material is used. It may be arranged so as to be sandwiched between two ferrite plates.

[0041]

According to the present invention, a small ferrimagnetic material
Even when using the inductors of the first and second center electrodes
Since the input and output impedances can be reliably matched by the series capacitor and the parallel capacitor, the insertion loss can be further reduced. Also, average
Since it is not necessary to increase the capacity of the column capacitor,
A wider frequency band can be achieved.

[0042]

Further , according to the present invention, the first and second middle
The crossing angle of the cardiac electrodes is specified within the range of 80 to 100 degrees.
The angle makes it possible to obtain a low insertion loss and a high irreversible characteristic.

Further , according to the present invention, the ferrimagnetic material is
By adopting a polygonal plate shape, it is possible to increase the magnetic coupling distance between the first and second center electrodes with respect to the ferrimagnetic body of the first and second center electrodes, and further to increase the magnetic coupling distance with respect to the ferrimagnetic body. When the first and second center electrodes are wound, the winding is facilitated, and even if the ferrimagnetic body is small, low insertion loss and high irreversible characteristics can be obtained.

According to the present invention, the magnet has a rectangular parallelepiped shape.
In this non-reciprocal circuit element having a rectangular parallelepiped shape as a whole, the strength of the static magnetic field with respect to the ferrimagnetic material can be further increased within a limited volume, the insertion loss is low, and the high non-reciprocal characteristic is achieved. Is obtained. Further, since it can be constituted by a method of cutting out from a plate-shaped or rectangular parallelepiped magnetic material, its manufacture becomes easy.

Further , according to the present invention, the first and second middle
Place the core electrode, ferrimagnet, and magnet on the upper yoke and lower yoke.
Between the upper yoke and the lower yaw.
Since the first and second center electrodes and the capacitor are brought to the ground potential together with the yoke by being grounded, the shield is suppressed.

According to the invention described in claim 7, for example, by providing a non-reciprocal circuit element having an isolation characteristic in the output section of the oscillation circuit or the input section of the filter, communication with low loss and stable characteristics can be achieved. The device is obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an isolator according to a first embodiment.

FIG. 2 is an exploded perspective view of the isolator.

FIG. 3 is a perspective view of a main part of the isolator after assembly.

FIG. 4 is a circuit diagram for explaining the operation principle of the isolator.

FIG. 5 is a diagram showing an example of impedance matching of the isolator.

FIG. 6 is a diagram showing an example of frequency characteristics of the isolator.

FIG. 7 is a block diagram showing a configuration of a main part of a high-frequency circuit device according to a second embodiment.

FIG. 8 is a circuit diagram of a conventional isolator.

FIG. 9 is a diagram showing an example of impedance matching in a conventional isolator.

FIG. 10 is a diagram showing an example of frequency characteristics in an impedance mismatched state with an isolator having a conventional structure.

[Explanation of symbols] 1-ferrite assembly 2-upper yoke 3- Magnet 4- Lower yoke 5-substrate 10-ferrite plate 11-first center electrode 12-second center electrode 50-ground electrode 51-input terminal electrode 52-Output terminal electrode

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-11-205016 (JP, A) JP-A-4-172702 (JP, A) JP-A-10-284907 (JP, A) JP-A-52-1 134349 (JP, A) JP 41-11290 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01P 1/36 H01P 1/383

Claims (2)

(57) [Claims] 1. A first and a second center electrodes, each having one end grounded, intersecting each other, a ferrimagnetic material close to the first and second center electrodes, and a static magnetic field with respect to the ferrimagnetic material. And a series capacitor connected in series between the other end of the first and second center electrodes and the input terminal and the output terminal, respectively, and the other end of the first and second center electrodes and the ground. And parallel capacitors connected in parallel between
The irreversible circuit element comprising a, the crossing angle of the first and second central electrode 80 degrees 10
Within a range of 0 degree, the ferrimagnetic material has a rectangular parallelepiped shape, the magnet has a rectangular parallelepiped shape, and the first and second center electrodes, the ferrimagnetic material, and the front portion.
When the magnet is placed between the upper and lower yokes,
And ground the upper and lower yokes and wrap the first and second center electrodes around the ferrimagnetic material.
The impedance of the first and second center electrodes viewed from the other end.
Smith, whose center is the normalized impedance
Greater than equal conductance circle through the center of the chart
By placing the parallel capacitor on the conductance circle and connecting the parallel capacitor,
The impedance seen from the connection position to the center electrode is
The impedance position of the center electrode on the Smith chart
From the Smith chart along the equal conductance circle
Move toward the heart, and by connecting the series capacitor, the input terminal and
The impedance seen from the output terminal is the parallel capacitor
From the impedance position due to the connection of the
Move to the center of the Smith chart along the circle of resistance
So that the parallel capacitor and the series capacitor
A non-reciprocal circuit element that defines the capacity of each . 2. A high-frequency circuit device using the nonreciprocal circuit element according to claim 1 .